GB2224863A - Electronic programmable thermostat for room air conditioning unit - Google Patents

Abstract

A programmable thermostat 45 is disposed at a location remote from a window air conditioning unit 10 controlled thereby. The thermostat has a temperature sensor 35 which itself is optionally remote from the thermostat. The thermostat may be programmed by a hand held remote control. The thermostat has a controller which selectively controls the on/off state of the air conditioning unit 10 in response to (1) a comparison of the time of day with program times stored in the memory to access a corresponding control temperature stored in the memory and (2) a comparison of the ambient temperature sensed by the sensor 35 and the control temperature stored in the memory. The system may log use of the air conditioner and indicate when the filter needs changing. <IMAGE>

Description

ELECTRONIC PROGRAMMABLE THERMOSTAT FOR A ROOM AIR CONDITIONING UNIT BACKGROUND OF THE INVENTION The present invention generally relates to air conditioning units and, more particularly, to an electronic programmable thermostat for a window air conditioning unit.

Window air conditioning units provide a viable alternative to central air conditioning systems in apartment buildings and offices which lack such central systems and in homes where it is either impractical or prohibitively expensive to install them. An important consideration in the purchase and installation of such a room air conditioning unit is the cost of operating the unit. An inefficiently operated air conditioner can result in substantial energy costs.

Generally, room air conditioning units are switched on as needed to cool the room in which the unit is located. However, such a method of operation can result in inefficient air conditioning use and increased energy costs. For example, a user may forget to switch of f the air conditioner, resulting in a waste of energy, particularly when the room is unoccupied. A user may also forget to switch on his air conditioner, resulting in discomfort while the unit is bringing the temperature down to a comfortable level.

Additional problems may arise when an air conditioning unit is utilized to cool a room by a particular time. This situation may occur, for example, when the air conditioner is used in a bedroom to cool the room overnight while the occupant sleeps. The user may turn on the air conditioner when he or she gets home from work at, for example, 6:00 p.m., in order that the room be cool by the time he or she retires at 11:00 p.m. However, it may only be necessary to turn on the air conditioner at 10:15 p.m. to sufficiently cool the room by 11:00 p.m.

Thus the energy used in cooling the room from 6:00 p.m. to 10:15 p.m.

is wasted.

In addition, it is also desirable to provide a user with different information related to the air conditioner operation. For example, the user may want to know how long his air conditioner operates on a daily or weekly basis or how long the air conditioning filter has been in use in order to calculate the operating costs and, if necessary, implement energy conservation efforts. The user may also desire information related to air conditioner filter use.

It is also desirable that a device which provides these features be compatible with existing and previously installed air conditioning units.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a programmable thermostat for use with a window air conditioning unit.

It is another object of the present invention to provide such digital progammability in a thermostat which is compatible with existing and previously installed air conditioning units.

It is still another object of the present invention to provide an air conditioning system which may be operated in an energy efficient manner.

According to the present invention, a programmable thermostat is provided for a window air conditioning unit which regulates the temperature within a predetermined volume of space. The programmable thermostat is disposed at a location remote from the window air conditioning unit. The programmable thermostat includes a sensor for sensing the ambient temperature within the predetermined volume of space and a timer for generating the current time of day. A memory is included for storing a plurality of program times and a plurality of control temperatures corresponding to the program times.

A controller selectively controls the on/off state of the individual air conditioning unit in response to (1) a comparison of the current time of day with the program times stored in the memory to access the corresponding current control temperature stored in the memory and (2) a comparison of the current ambient temperature sensed by the sensor and the current control temperature stored in the memory to generate a switching control signal for coupling power to the window air conditioning unit.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the invention becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

Figure 1 is an illustration showing an air conditioning system including a remote programmable thermostat in accordance with the present invention.

Figure 2 illustrates a plug-in thermostat in accordance with one embodiment of the present invention.

Figure 3 shows a hand-held remote which may be used with the plug-in thermostat of the present invention.

Figure 4 is a hardware diagram of a thermostat in accordance with an embodiment of the present invention.

Figure 5 is a flow chart illustrating the operation of a thermostat in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 1 is a schematic diagram illustrating the use of a plug-in programmable thermostat of the present invention with a window air conditioner. Window air conditioner 10 includes a power cord 15 with plug 20 on one end thereof. Plug 20 is plugged into switched AC receptacie 25 of thermostat 45. The switching of AC receptacle 25 is controlled by thermostat 45. AC receptacle 25 selectively supplies power to air conditioner 10 in response to time and temperature data input by the user to thermostat 45 as discussed in more detail below.

Thermostat 45 includes remote temperature sensor 35 which may detached from the thermostat housing in order to position the sensor in various parts of the room. Remote temperature sensor 35 is prer- erably a thermister-type temperature sensor although the invention is not limited in this respect. Extension cord 30, preferably having a length of several feet, couples remote sensor 35 to thermostat 45.

Extension cord 30 may be coiled around a back portion of thermostat 45 when the remote sensor is attached to the thermostat housing. In an alternative embodiment, a temperature sensor may simply be provided inside or outside the thermostat. Remote sensor 35 permits measurement of an ambient room temperature which is more representative of the actual temperature sensed by an occupant of the room. Thus, remote sensor 35 may be positioned in a central portion of a room and ambient temperature determination is not confined to the walls or corners of a room which can provide an inaccurate measurement of the temperature sensed by room occupants. Thermostat 45 is adapted to be capable of plugging in to a standard AC wall outlet 40. Thermostat 45 may be powered by AC line power or DC battery power.

Figure 2 illustrates in more detail the features of plug-in programmable thermostat 45. Thermostat 45 has a display 50 which includes a digital clock with a liquid crystal display which displays the time of day in hours and minutes. an A.M. or P.M. indicator, day of the week, current room temperature, current program number, a low battery indicator, and an indicator when the air conditioner is on.

Keys 55 include an HOUR, a MIN, and a DAY key for respectively entering the hour of the day, the minute of the day and the day of the week. The PROG key is used for reviewing or entering the various program cycles. The HOLD key permits a user to override programmed temperature settings for an extended period of time by keying in a new temperature setting. The HOLD key also permits manual operation of the thermostat. The RETURN key returns display 50 to the current time and temperature. If pressed for three seconds, the RETURN key also returns thermostat 45 from a manual override mode. The USAGE key is an energy monitor key which recalls and displays energy usage for the present day and the previous day. Alternatively, energy usage may be displayed for the present week, past week or any other interval of time. The USAGE key is also used to reset the energy monitor counter back to zero.When the USAGE key is depressed for three seconds or more the counter will reset to zero. Display 50 preferably shows energy usage in hours and minutes, although displays of kilowatts, kilowatt hours and accumulated cost may also be provided. Filter review key 55A may be depressed to review filter usage in hours and minutes. Filter review key 55A also resets the filter usage counter to zero if depressed for three or more seconds. The arrow push buttons are used to raise or lower temperature settings.

Additional keys shown in Figure 2 may also be included. A temperature SPAN key may be used to set high and low temperature limits to better control the on and off cycling of air conditioner 10 for better control of the room temperature. Such feature keys are also shown, in the hand-held remote of Figure 3 discussed in detail below.

Thermostat 45 may be bypassed by use of function switch 57.

When switch 57 is in the bypass position, thermostat 45 no longer controls the air conditioner operation. Control is then transferred to the thermostat of the air conditioning unit itself. In this mode thermostat 45 continues to display the time and the room temperature.

Thermostat IS can also be programmed to act as a timer. In this mode, the plug-in thermostat 45 behaves as a timer and does not control the room temperature. The air conditioner is switched on and off according to various program times and thermostat 45 is capable of accepting separate time programs exclusively for the timer mode.

Temperature control is then performed by the thermostat of the air conditioner unit.

Thermostat 45 may also be designed to incorporate a control timer mode. When the thermostat is in this mode, the timer will activate and deactivate the unit as per the program. In an active condition, thermostat 45 will control the room temperature to a single programmed comfort temperature while in the unactivated state the air conditioner will be turned off completely.

These various features and the method of programming thermostat 45 will now be discussed in detail. In order to set the current time and day of week, the HOUR and MIN keys are respectively depressed until the correct hour and minutes are displayed on display 50. The day is set by repeatedly depressing the DAY key until the correct day appears.

The thermostat may be programmed by use of the PROG key.

After depressing the PROG key, the clock may be advanced to the desired program time by use of the hour and minute keys. The program temperature may be set by use of the arrow keys to raise and lower the temperature. Subsequent depressions or the PROG key permit additional programs to be entered into the thermostat.

Programmability of the plug-in thermostat is a powerful and important feature of the present invention. Programmability permits users to program a plurality of temperature settings for a plurality of programmed times. Programmability permits high efficiency operation and can result in substantial energy savings. For example, if an air conditioning unit is utilized to cool the living room of a house or apartment, the on/off switching of the air conditioning unit may be precisely determined. It is desirable to have the room cooled during times of occupancy but in the interest of energy conservation, it is further desirable to have the unit switched off completely or to have the unit maintain some temperature higher than the comfort temper- ature during times of non-occupancy.This latter alternative of maintaining the some temperature is particular by important so as not to damage any plants or expensive furniture. The present invention permits the user to program a cooling schedule such that the air conditioner may be switched on at, for example, 5:00 p.m. to cool the room to the programmed temperature of 760F by 6:00 p.m. when the user returns home from work. The programmed temperature of 760 may be maintained by the thermostat until 11:00 p.m. when the occu pants go to bed. The air conditioner may then be programmed to maintain the living room at, for example, 80e overnight in order to conserve energy. It may also be desirable to have the temperature lowered to 78 during some part of the morning, say T:30 a.m. to 9:00 a.m.The temperature may then be set-up to 85 during the day from 9:00 a.m. to S:00 p.m. in order to conserve energy. It is important that the temperature not be permitted to rise too much during the unoccupied periods or else the unit may require so much energy to bring the ambient room temperature down to the program temperature that energy savings are eliminated.

The various programs may be created and modified to suit the user's lifestyle. Different programs may be entered to control the air conditioner over weekends, for example, when a user is likely to be home at different hours.

The arrow keys may be used to override a programmed temperature setting. The override mode permits a user to instruct the thermostat to ignore program settings without requiring the thermostat to be reprogrammed. Using temporary manual override, the temperature setting may be raised or lowered to a temporary setting until the next program time. The temperature may be changed by use of the arrow keys and the thermostat will remain in manual override until the next program time. The thermostat may be permanently manually overridden for an extended period of time, such as a vacation, by following the above procedure and then depressing the HOLD key. To return back to the programmed temperature scheme from a permanent manual override mode, the RETURN key may be depressed for three seconds.Alternatively, the override mode may be activated for some predetermined time interval such as one hour, two hours, et cetera.

An energy monitoring operation measures and logs the amount of time air conditioner 10 operates over a given time interval. With the USAGE key, the total energy usage may be displayed for the present day (as of 12:01 AM), or the previous day (12:01 AM through midnight). By monitoring the energy used on a daily basis, the user can gradually adjust the temperature settings and monitor the effect of energy conservation efforts. The energy monitor feature can further be extended to monitor energy usage for the present week, the previous week, and the total cumulative use, as noted above. A single depression of the USAGE key displays the amount of time in hours and minutes that air conditioner 10 has operated on the present day. A second depression of the USAGE key displays the amount of time the system operated on the previous day.Subsequent key depressions may display energy usage for the present week, previous week, and total cumulative use. Alternatively, display 50 may indicate the number of kilowatts, kilowatt hours, or cumulative cost of running the air conditioner. The time period over which the actual usage is logged may alternatively be a week or any other length of time.

A hardware diagram of thermostat 45 is shown in Figure 4.

Thermostat 45 includes single chip microcomputer 47 having a Read Only Memory (ROM) for software and a Random Access Memory (RAM) for data storage. The component blocks bounded by the broken lines in Figure 4 are contained within microcomputer 47.

System clock generator 2 generates the timing signal for the microcomputer in response to system clock generating element 1.

Clock generating element 1 may, for example, be a 32768 cycle crys tal. The timing signal generated by clock generator 2 is divided repeatedly by divider 3 to generate a one second timing signal for real time clock base 4. The real time clock tracking of clock base 4 is necessary for the programming (software) features of the thermostat.

Real time clock base 4 also provides a signal to display controller 6 which generates the time of day display for LCD 5. Low battery level detector 7 determines when new batteries are needed for the thermostat and provides a signal to display controller 6 to illuminate or flash a low battery prompt on LCD 5.

Component block 12 is a program control data input which is preferably keys on programmable thermostat 45. The program data input to the thermostat 45 via these keys is stored in memory 11.

Each second, microcomputer 47 compares the program times stored in memory 11 and the real time to determine whether a new cooling setpoint temperature is required. When the real time matches a program time, the program temperature corresponding to that program time becomes the reference temperature against which the ambient room temperature is compared by comparator 18 to determine the operating state of air conditioner 10. When certain onloff criteria related to the program temperatures are reached, an on/off switching signal is sent to output controller 21 to control the operating state of air conditioner 10.

The operation of thermostat 45 will be explained with refer ence to the flow chart Figure 5. Upon power-up, all data in the mem ory is cleared and the output is off. At step 110, default values are assigned to the time-temperature program. At step 112, default values are assigned to the clock and temperature control limits. Next, at step 113, the display is updated for the existing mode. After each onesecond real time interval, the exact ambient temperature is evaluated at step 114. The real time clock display of day, hour, minutes, and seconds is updated at step 115. At step 116, if the output control is in the ON state, the update usage counter is incremented at step 116. Otherwise, control immediately passes to step 117. The update usage counter permits the energy monitoring function described above.

At step 117, a determination is made if the thermostat is in normal clock mode (described below). If so, a determination is made at step 118 whether permanent override is in effect. If permanent override is not in effect, a determination is made at step 120 whether the program time is equal to the real clock time. If so, the associated program temperature is set as the prevailing control temperature at step 121. If not, control passes to step 123 where a comparison is made between the ambient temperature and the prevailing control temperature.

If, at step 118, permanent override is in effect, control immediately passes to step 123. If the ambient temperature is such as to require the switching on of the air conditioning unit, the air conditioner is switched on at step 124 after an appropriate predetermined time period and control returns to step 113. It the ambient temperature is not such as to require the switching on of the air conditioning unit. a determination is made at step 127 whether the ambient temperature is such that the air conditioning should be switched off. If so, the air conditioning unit is switched off after an appropriate pre determined time period at step 128 and control returns to step 113. If not, control immediately returns to step 113.

Normal clock mode refers to the thermostat mode in which the current time and current temperature are displayed. However, when the thermostat is in programming mode, override mode, usage review mode, et cetera, the thermostat is no longer in the normal clock mode. Thus, updating the temperature, the on/off switching of the air conditioner, the checking of program temperature, et cetera, are performed in normal clock mode only. In other words, for safety reasons, no decisions are made while a user is programming the thermostat.

If, at step 117, the thermostat is not in normal clock mode, control passes to step 130 where a determination is made whether the time is up to normal clock mode. U not, control passes back to step 113. If so, the thermostat converts back to normal clock mode at step 131 and control subsequently passes back to step 113.

The microprocessor for the thermostat also checks for any key entries by the user at step 135. Figure 5 illustrates several modes which the thermostat may be entered by key operations. A time set mode permits setting of the hour, minute, and day. An override mode permits a permanent or temporary override of the temperature set tings. A usage review mode permits a user to view the amount of time the air conditioning unit has been on during some predetermined time interval, e.g. a day or a week. A program set mode permits the user to set program times and temperatures. Each of the above modes is active for 8 seconds after the respective key operations.

The return mode returns the thermostat to the normal clock mode and control returns to step 113. After the 8 second active period, control also returns to step 113.

The thermostat also preferably includes a filter usage function for logging and displaying the total usage ge of the air conditioner filter.

The filter time log may be displayed in hours or in hours and minutes.

The thermostat preferably includes an automatic reminder after the filter has been in use for some predetermined time period. For example, at 500 hours the word "FILTER" may appear on the display reminding the user to change the filter and reset the counter back to zero. The "FILTER" display will continue if the counter is not set back to zero. Such a reminder serves as an indication to clean or replace the air conditioning filter for maximum efficiency of operation and increased energy savings.

The elapsed filter usage and the energy monitoring system may be maintained by conventional techniques such as counters or timers in the thermostat. Other techniques may also be used. In addition, it is possible, for example, for the filter monitor to comprise a decrementing counter which may be preset by the user for a predetermined time period equal to the filter lifetime. The LCD dis play may provide an indicator when the counter reacnes 0 or some other predetermined value. Alternatively, an audible warning may be provided. Such a pre-programmed time period may also be utilized to warn the user by a visual display or audible warning of excess use of the air conditioner. An additional built-in timer may be provided to prevent damage to the air conditioner compressor caused by rapid cycling by providing a predetermined delay, four minutes for example, before it will restart.This same delay may be provided upon power being restored after a main power failure. Whenever the main power is interrupted or fails for an extended period of time, battery power may be used to retain the programs and current time.

The thermostat may also include a temperature span feature.

The thermostat may be programmed to cycle when the temperature rises 20 above or 10 below the current prevailing temperature setting. For example, if the air conditioner is programmed to maintain a 750 setting, the unit will cycle on when the room temperature reaches 77C (20 above the set point of 75 ) and stay on until the temperature is 740 (10 below the set point of 750) The programmable plug-in thermostat may be addressed by an infrared or RF-type hand-held remote. Such a remote is shown in Figure 3 and is similar in operation to a hand-held remote commonly used with televisions and stereos. Transmission of signals from the remote to the plug-in programmable thermostat is conventional and is not described herein in any detail. Remote 70 includes LCD 65 for displaying information such as day, time, and temperature settings.

Remote 70 also includes a plurality of keys. The remote may be programmed and the information transmitted to the plug in thermostat.

The use of a hand-held remote facilitates programming, especially where the plug in unit is located at an AC outlet which may be somewhat inaccessible. Programming steps utilizing hand-held remote 70 are the same as those described above for thermostat 45.

The invention has been described in detail in connection with the preferred embodiments. These embodiments, however, are merely for example only and the invention is not limited thereto. It will be easily understood by those skilled in the art that other variations and modifications can easily be made within the scope of this invention as defined by the appended claims.

Claims (20)

1. A programmable thermostat for use with a window air conditioning unit which regulates the temperature within a predetermined volume of space, said programmable thermostat disposed at a location remote from said window air conditioning unit and at least including sensor means for sensing the ambient temperature within the predetermined volume of space, timing means for generating the current time of day, memory means for storing a plurality of program times and a plurality of control temperatures corresponding to the program times, and control means for selectively controlling the on/off state of said individual air conditioning unit in response to (1) a comparison of the current time of day with the program times stored in said memory means to access the corresponding current control temperature stored in said memory means and (2) a comparison of the current ambient temperature sensed by said sensor means and the current control temperature stored in said memory means to generate a switching control signal for coupling power to said window air conditioning unit.

2. The programmable thermostat according to claim 1 wherein said sensor means may be positioned at a location remote from said programmable thermostat.

3. The programmable thermostat according to claim 1 further including display means for at least displaying the day, time of day, and current ambient temperature.

4. The programmable thermostat according to claim 1 further including energy monitoring means for monitoring the amount of time said air conditioning unit is operated over a predetermined time interval.

5. The programmable thermostat according to claim 1 wherein said programmable thermostat is adapted to be plugged into an A.C. wall outlet.

6. The programmable thermostat according to claim 1 fur ther including filter monitoring means for monitoring the amount of time an air filter for said air conditioning unit has been installed.

7. The programmable thermostat according to claim 1 wherein said sensor means comprises a thermistextype temperature sensor.

8. The programmable thermostat according to claim 1 further including span control means for selectively controlling the temperature span limits at which said window air conditioning unit switches on or off.

9. The programmable thermostat according to claim 1 fur- ther including timer means for selectively switching said air conditioning unit on or off in accordance only with the program times stored in said memory means.

10. The programmable thermostat according to claim 1 further including by-pass means for transferring the on/off switching control ot said air conditioning unit to a thermostat contained within said air conditioning unit.

11. The programmable thermostat according to claim 1 further including override means for overriding the control temperatures stored in said memory means.

12. The programmable thermostat according to claim 11 wherein said override means may be enabled for a predetermined time interval.

13. A control system for a window air conditioning unit which regulates the temperature within a predetermined volume of space, said control system including: a programmable thermostat disposed at a location remote from said window air conditioning unit, said programmable thermostat at least including sensor means for sensing the ambient temperature within the predetermined volume of space, timing means for generating the current time of day, memory means for storing a plurality of program times and a plurality of control temperatures corresponding to the program times, and control means for selectively controlling the on/off state of said individual air conditioning unit in response to (1) a comparison of the current time of day with the pro gram times stored in said memory means and (2) a comparison of the current ambient temperature sensed by said sensor means and the current control temperature stored in said memory means to generate a switching control signal for coupling power to said window air conditioning unit; and an wireless hand-held remote control capable of addressing said programmable thermostat in order to provide access to said programmable thermostat from a remote location.

14. The control system according to claim 13 wherein said sensor means may be positioned at a location remote from said programmable thermostat and said window air conditioning unit.

15. The control system according to claim 13 wherein said wireless hand-held remote control comprises an infrared remote control.

16. The control system according to claim 13 wherein said wireless hand-held remote control comprises an RF-type remote control.

17. A control system for a window air conditioning unit which regulates the temperature within a predetermined volume of space, said control system including: a programmable thermostat disposed at a location remote from said window air conditioning unit for selectively controlling the on/off switching of said window air conditioning unit in response to comparisons between the ambient temperature and control temperatures programmed in said thermostat; sensor means disposed at a location remote from said programmable thermostat and said window air conditioning unit for sensing the ambient temperature within the predetermined volume of space; and a wireless hand-held remote control capable of addressing said programmable thermostat in order to provide access to said programmable thermostat from a remote location.

18. The control system according to claim 17 wherein said sensor means comprises a thermister-type temperature sensor.

19. A programmable thermostat constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

20. A control system for a window air conditioning unit constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.